I have saved a bunch of CGContextRefs and I want to draw all of these out in the drawRect portion of my UIView. How can I do this?
Here is one way:
- (void)drawRect:(CGRect)rect {
CGImageRef newImg = CGBitmapContextCreateImage(ctx1);
[[UIImage imageWithCGImage:newImg] drawInRect:rect];
CGImageRelease(newImg);
CGImageRef newImg = CGBitmapContextCreateImage(ctx2);
[[UIImage imageWithCGImage:newImg] drawInRect:rect];
CGImageRelease(newImg);
}
Related
I was wondering if it's possible to "extract" a part of UIImageView.
For example, I select using Warp Affine a part of the UIImageView and I know the selected part frame.
like in this image:
Is it possible to get from the original UIImageView only the selected part without losing quality?
Get the snapshot of the view via category method:
#implementation UIView(Snapshot)
-(UIImage*)makeSnapshot
{
CGRect wholeRect = self.bounds;
UIGraphicsBeginImageContextWithOptions(wholeRect.size, YES, [UIScreen mainScreen].scale);
CGContextRef ctx = UIGraphicsGetCurrentContext();
[[UIColor blackColor] set];
CGContextFillRect(ctx, wholeRect);
[self.layer renderInContext:ctx];
UIImage* image = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
return image;
}
#end
then crop it to your rect via another category method:
#implementation UIImage(Crop)
-(UIImage*)cropFromRect:(CGRect)fromRect
{
fromRect = CGRectMake(fromRect.origin.x * self.scale,
fromRect.origin.y * self.scale,
fromRect.size.width * self.scale,
fromRect.size.height * self.scale);
CGImageRef imageRef = CGImageCreateWithImageInRect(self.CGImage, fromRect);
UIImage* crop = [UIImage imageWithCGImage:imageRef scale:self.scale orientation:self.imageOrientation];
CGImageRelease(imageRef);
return crop;
}
#end
in your VC:
UIImage* snapshot = [self.imageView makeSnapshot];
UIImage* imageYouNeed = [snapshot cropFromRect:selectedRect];
selectedRect should be in you self.imageView coordinate system, if no so then use
selectedRect = [self.imageView convertRect:selectedRect fromView:...]
Yes, it's possibile.First you should get the UIImageView's image, using this property:
#property(nonatomic, retain) UIImage *image;
And NSImage's :
#property(nonatomic, readonly) CGImageRef CGImage;
Then you get the cut image:
CGImageRef cutImage = CGImageCreateWithImageInRect(yourCGImageRef, CGRectMake(x, y, w, h));
If you want again a UIImage you should use this UIImage's method:
+ (UIImage *)imageWithCGImage:(CGImageRef)cgImage;
PS: I don't know how to do it directly, without convert it to CGImageRef, maybe there's a way.
I want to know, how can I erase a custom rect (with, for example, an UIView in IB or something else) of an UIImageView in order to display an other UIImageView positioned underneath.
I didn't manage to do it using some response in the forum...
This will clear a rect in an image:
- (UIImage *)clearRect:(CGRect)rect inImage:(UIImage *)image {
if (UIGraphicsBeginImageContextWithOptions != NULL)
UIGraphicsBeginImageContextWithOptions([image size], NO, 0.0);
else
UIGraphicsBeginImageContext([image size]);
CGContextRef context = UIGraphicsGetCurrentContext();
[image drawInRect:CGRectMake(0.0, 0.0, [image size].width, [image size].height)];
CGContextClearRect(context, rect);
UIImage *result = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
return result;
}
Just load your image and clear the rects before assigning it to the image view:
UIImage *image = [UIImage imageNamed:#"Image.png"];
UIImage *maskedImage = [self clearRect:CGRectMake(10.0, 10.0, 50.0, 50.0) inImage:image];
[imageView setImage:maskedImage];
probably not the best solution but you can do the other way and take the 4 parts around the rect separately and combine them afterwards without the inner rect. You would repeat this as long as you have rect's to crop out.
You cannot clear the UIImageView itself because this just draws the UIImage. So you have erase the rect in the UIImage. Create a bitmap context, draw the image into it. Erase the part you want to "see through" with CGContextClearRect. When create a new new image from the bitmap context.
I'd like to combine two UIImages, one stretchable and one "normal" one. The problem is that if I merge the Images using the UIGraphicsImageContext, the scond image is also stretched (it is on top of the first one as it should be, but stretched). Does anybody know how to avoid this?
Thanks a lot!
calls from my ViewController:
UIImage *stretchImage = [[UIImage imageNamed:#"stretchableLeft.png"] stretchableImageWithLeftCapWidth:0.0 topCapHeight:16.0];
stretchImage = [self imageWithImage:stretchImage scaledToSize:CGSizeMake(64.0, 64.0)];
stretchImage = [self mergeImageWithImage:stretchImage secondImage:[UIImage imageNamed:#"topImage.png"]]; // only 40x40 Px
the two methods are:
- (UIImage*)imageWithImage:(UIImage*)image scaledToSize:(CGSize)newSize
{
UIGraphicsBeginImageContext( newSize );
[image drawInRect:CGRectMake(0,0,newSize.width,newSize.height)];
UIImage* newImage = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
return newImage;
- (UIImage*)mergeImageWithImage:(UIImage *)image secondImage:(UIImage *)image2
{
UIGraphicsBeginImageContext(image.size);
[image drawInRect:CGRectMake(0,0,image.size.width,image.size.height)];
[image2 drawInRect:CGRectMake(10,10,image.size.width,image.size.height) blendMode:kCGBlendModeNormal alpha:1.0];
UIImage *newImage = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
return newImage;
}
I think the issue is that you're asking both images to draw in the full rectangle. That is causing your second image to stretch.
Try using the image2.size for image2 when merging the images. You'll have to adjust the placement using the x/y coordinate when drawing the rectangle.
- (UIImage*)mergeImageWithImage:(UIImage *)image secondImage:(UIImage *)image2
{
UIGraphicsBeginImageContext(image.size);
[image drawInRect:CGRectMake(0,0,image.size.width,image.size.height)];
[image2 drawInRect:CGRectMake(10,10,image2.size.width,image2.size.height) blendMode:kCGBlendModeNormal alpha:1.0];
UIImage *newImage = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
return newImage;
}
I've been trying to use a method commonly used to resize an image. Without using this method, here is the code that takes a url of an image.
NSData *data = [NSData dataWithContentsOfURL:url];
UIImage *img = [[UIImage alloc] initWithData:data];
cell.imageView.image = img;
This works fine. But when I try to use this method:
-(UIImage*)imageWithImage:(UIImage*)image scaledToSize:(CGSize)newSize;
{
UIGraphicsBeginImageContext( newSize );
[image drawInRect:CGRectMake(0,0,newSize.width,newSize.height)];
UIImage* newImage = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
return newImage;
}
and call it using this:
UIImage *scaledImage = [self imageWithImage:img scaledToSize:CGSizeMake(10.0f,10.0f)];
then putting into my table like this:
cell.imageView.image = scaledImage;
Nothing shows up. Is there something I'm missing here?
This is similar to Exporting customized UITableViewCells into UIImage
Here's what you need to do in your -imageWithImage:scaledToSize: method, modified from my answer to that question:
-(UIImage*)imageWithImage:(UIImage*)image scaledToSize:(CGSize)newSize
{
// Create a bitmap context.
CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();
CGContextRef bitmapContextForScaledImage = CGBitmapContextCreate(nil, newSize.width, newSize.height, 8, 0, colorSpace, kCGImageAlphaNone);
CGColorSpaceRelease(colorSpace);
// Draw the image's layer into the context.
UIImageView * imageView = [[UIImageView alloc] initWithImage:image];
[imageView.layer renderInContext:bitmapContextForCell];
[imageView release];
// Create a CGImage from the context.
CGImageRef cgScaledImage = CGBitmapContextCreateImage(bitmapContextForScaledImage);
// Create a UIImage from the CGImage.
UIImage * scaledImage = [UIImage imageWithCGImage:cgScaledImage];
// Clean up.
CGImageRelease(cgScaledImage);
CGContextRelease(bitmapContextForScaledImage);
return scaledImage;
}
Here's the code I have but it's crashing ... any ideas?
UIImage *tempImage = [[UIImage alloc] initWithData:imageData];
CGImageRef imgRef = [tempImage CGImage];
[tempImage release];
CGFloat width = CGImageGetWidth(imgRef);
CGFloat height = CGImageGetHeight(imgRef);
CGRect bounds = CGRectMake(0, 0, width, height);
CGSize size = bounds.size;
CGAffineTransform transform = CGAffineTransformMakeScale(4.0, 4.0);
UIGraphicsBeginImageContext(size);
CGContextRef context = UIGraphicsGetCurrentContext();
CGContextConcatCTM(context, transform);
CGContextDrawImage(context, bounds, imgRef);
UIImage *image = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
What am I missing here? Basically just trying to scale image up and crop it to be same size as original.
Thanks
The problem is this line:
CGImageRef imgRef = [tempImage CGImage];
Or more precise, the direct follow-up of this line:
[tempImage release];
You are getting a CF object here, the CGImageRef. Core Foundation object only have the retain/release memory management, but no autoreleased objects. Hence, when you release the UIImage in the second row, the CGImageRef will be deleted as well. And this again means that it's undefined when you try to draw it down there.
I can think of three fixes:
use autorelease to delay the release of the image: [tempImage autorelease];
move the release to the very bottom of your method
retain and release the image using CFRetain and CFRelease.
Try this one:
-(CGImageRef)imageCapture
{
UIGraphicsBeginImageContext(self.view.bounds.size);
[self.view.layer renderInContext:UIGraphicsGetCurrentContext()];
UIImage *viewImage = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
CGRect rect= CGRectMake(0,0 ,320, 480);
CGImageRef imageRef = CGImageCreateWithImageInRect([viewImage CGImage], rect);
return imageRef;
}
use the below line whenever you want to capture the screen
UIImage *captureImg=[[UIImage alloc] initWithCGImage:[self imageCapture]];